Neurobehavioral deficits associated with PCB in 7-year-old children prenatally exposed to seafood neurotoxicants.

Prenatal exposure to polychlorinated biphenyls (PCBs) was examined by analysis of cord tissue from 435 children from a Faroese birth cohort. Analysis of 50 paired cord blood samples showed excellent correlation with the cord tissue concentration (r=.90). Among 17 neuropsychological outcomes determined at age 7 years, the cord PCB concentration was associated with deficits on the Boston Naming Test (without cues, two-tailed P=.09 not adjusted for mercury; with cues, P=.03), the Continuous Performance Test reaction time (P=.03), and, possibly, on long-term recall on the California Verbal Learning Test (P=.15). The association between cord PCB and cord-blood mercury (r=.42) suggested possible confounding. While no PCB effects were apparent in children with low mercury exposure, PCB-associated deficits within the highest tertile of mercury exposure indicated a possible interaction between the two neurotoxicants. PCB-associated increased thresholds were seen at two of eight frequencies on audiometry, but only on the left side, and no deficits occurred on evoked potentials or contrast sensitivity. The limited PCB-related neurotoxicity in this cohort appears to be affected by concomitant methylmercury exposure.

Concentration-dependent changes of PCB patterns in fish-eating mammals: structural evidence for induction of cytochrome P450.

Data sets on CB concentrations in fish-eating mammals from five laboratories were combined to test and refine a pharmacokinetic model. Clear differences in PCB patterns were observed between species. The ability to metabolize chlorobiphenyl (CB) congeners with vicinal H-atoms only in the ortho- and meta-positions and with one ortho-chlorine substituent generally increased in the order otter < cetaceans (harbor porpoise, common dolphin) < phocid seals (harbor and grey seal), but the metabolism of congeners with vicinal H-atoms in the meta- and para-positions and with two ortho-chlorines increased in the order cetaceans < seals < otter. Both categories of congeners are probably metabolized by different families of cytochrome P450 (1A and 2B) of which levels apparently differed between the cetaceans, the pinnipeds, and the otter. Within-species CB patterns differed in a concentration-dependent manner. The induction of cytochrome P450 enzymes offers the most likely explanation for this phenomenon, but starvation could have a similar effect on occasion.

Patterns of chlorinated biphenyl congeners in harbor seals (Phoca vitulina) and in their food: statistical analysis.

Patterns of chlorinated biphenyl (CB) congeners have been compared in two groups of samples, namely blood samples from harbor seals (Phoca vitulina) and muscle tissue samples in the fish with which the seals were fed. The data originate from a Dutch controlled feeding study, performed in 1981 and 1983. The seals were living in captivity in two separate groups, and the fish samples were plaice (Pleuronectes platessa) from the Dutch part of the Wadden sea and mackerel (Scomber scombrus) from the Atlantic ocean. The levels of CB congeners were different in the two types of fish. The CB congener patterns of these four "matrices" were compared by analysis of principal components, and were found to be different in the two groups of harbor seals, which were fed the different types of fish. The corresponding CB congener patterns of the two groups of fish were also different. There was no indication for a relatively larger impact of biotransformation due to induction of isoforms of the cytochrome P450-system at the higher absolute CB congener levels in the Wadden sea group of seals compared to the Atlantic group of seals. The differentiation between the CB congener patterns in the two groups of seals in the Dutch study can be ascribed solely to different CB congener patterns in their food. The difference between CB congener patterns in the seals and in their diet can be explained by the structure-related biotransformation of the CB congeners in the harbor seal.

Distribution patterns of polychlorinated biphenyl congeners in harbor seal (Phoca vitulina) tissues: statistical analysis.

Tissue samples from five harbor seals (Phoca vitulina) have been analyzed for coplanar and other polychlorinated biphenyl (CB) congeners, in order to measure variations in levels and patterns of the CBs. Blubber samples contained the highest levels of CBs in all animals; kidney and liver were relatively high-level tissues. CB-153 and CB-138 were the most abundant CB congeners in all samples analyzed. Variations in the patterns of CB congeners in tissues were studied by principal component analyses and multivariate analysis of variance. The CB congener patterns in seals from different geographical regions had distinctly different patterns, whereas the patterns appeared quite similar in tissues within each seal. Based on multivariate analysis of variance, it was, however, possible to detect some systematic variation of the principal components with individual seals and with tissue type within the seals. The assessment of differences in CB congener patterns was possible by comparison to results obtained by repeated analyses of a quality control sample. The calculated dioxin toxic equivalents of the CB congeners followed the levels of the CB congeners, with the highest levels being found in the blubber samples.

Coplanar polychlorinated biphenyl congener levels and patterns and the identification of separate populations of harbor seals (Phoca vitulina) in Denmark.

Blubber samples from 21 harbor seals (Phoca vitulina), found dead on Danish beaches during the morbilli virus epidemic in 1988, have been analyzed for toxic coplanar chlorinated biphenyl (CB) congeners. The 21 samples consist of seven samples from 1-2-year-old animals (both males and females) from each of three geographical separate locations: The Limfjord, the Kattegat, and the Wadden Sea. The level of the CBs, defined as the sum of all the measured CB congeners, were highest in the samples from the Wadden Sea and lowest in the Limfjord samples. The quotient between highest level and lowest level was 4. Toxic equivalency factors given by Safe (1990) was used for calculation of the contribution to dioxin-like toxicity from the coplanar CB congeners, and the result was compared to literature data on polychlorinated dibenzo-p-dioxins and -dibenzofurans in harbor seal. CB congeners CB-118, CB-156, CB-157, and CB-105 were major contributors to sigma TEQ in all samples. The patterns of polychlorinated biphenyl congeners in harbor seals from the three locations were compared by principal component analysis. The two first principal components could separate the samples in groups corresponding to each of the three geographical locations. The geographical and biological variations were estimated from the data. It was shown, that the geographical variation was the largest. Possible reasons behind the geographical variation in CB congener patterns are discussed.